Lukaku missed one golden chance four minutes into his United debut, with his shot saved by Galaxy goalkeeper Brian Rowe.

However Mourinho was satisfied with Lukaku’s “unselfish” display in leading the line.

“Lukaku is a target man, he plays with his back to opponents,” Mourinho said. “A good thing today for me is to see that he’s a team player. He’s not selfish. He’s not obsessed with goals.

“He was not that worried about himself, he was worried about the improvement of the team.”

Rashford meanwhile reminded Mourinho of his eye for goal with a confident first-half display.

The teenager opened the scoring after only two minutes, punishing an error from Ariel Lassiter near the Galaxy penalty area to dart in on goal and place his finish beyond goalkeeper Jon Kempin.

The 19-year-old doubled his tally in the 20th minute, latching onto a clever pass from Juan Mata to make it 2-0.

– Rashford ‘still growing’ –

Mourinho later revealed that Rashford, who looks to have added a physical dimension to his game, was still growing.

“It’s just the natural evolution of a kid,” Mourinho said. “He’s already taller than when I arrived 13 months ago. He’s three centimeters taller. He’s put on some muscle but without any kind of specific work because his speed is his most important quality and we don’t want to lose that.”

Marouane Fellaini ensured United had a 3-0 lead at half-time tucking a low shot past the hapless Kempin after good work down the left flank by Jesse Lingard.

Mourinho changed his entire line-up at half-time, mirroring wholesale changes made by the Galaxy.

United got their fourth of the night on 67 minutes when Martial burst forward and threaded a pass to Mkhitaryan who made no mistake with a confident low strike.

Martial made it 5-0 five minutes later, rifling home Timothy Fosu-Mensah’s pullback.

Galaxy meanwhile, who had failed to register a single attempt on goal in the first half, bagged two late consolation goals through Mexico international Giovani Dos Santos.

Mourinho said the game had been “an amazing training exercise.”

“That’s what we need,” he said. “They gave us two different teams they gave people with intensity, so it was good for us.”

Mourinho was also satisfied with an experimental formation which saw him play with a three-man central defence.

“We tried a system that is not our main system,” he said. “We were working a few days on this to try to make the players feel a new experience in a new position and I’m really happy happy with that.

“It’s something we have to keep working and keep improving in case during the season we decided to play with three at the back. Maybe we want to do it more times.”

United travel to Utah to face Real Salt Lake in the second game of their US tour on Monday.